Process for preparation of pour depressants



May 31, 1966 s. ILNYCKYJ PROCESS FOR PREPARATION OF FOUR DEPRESSANTSFiled Jan. 4, 1962 Inventor Stephan llnyckyj By ()1 7 W Patent AttorneyUnited States Patent 3,254,063 PROCESS FOR PREPARATION OF POURDEPRESSANTS Stephen Ilnyckyj, Sarnia, Ontario, Canada, assignor to EssoResearch and Engineering Company, a corporation of Delaware Filed .lan.4, 1962, Ser. No. 164,248 11 Claims. (Cl. 260-873) The present inventionis concerned with the manufacture of improved pour depressants,particularly for use with middle distillates. The pour depressant of thepresent invention comprises copolymers of ethylene with up to about 50%by weight of an olefinically unsaturated aliphatic monomer containingfrom about 3 to 5 carbon atoms per molecule. The copolymers of aparticular average molecular weight are obtained by controlling theconditions of reaction. The preferred copolymer of the present inventionis a particular copolymer of ethylene and vinyl acetate.

The present application is a continuation-in-part of Ser. No. 1,838filed Ian. 5, 1960, US. Patent No. 3,093,623 entitled Process for theManufacture of Improved Pour Depressants for Middle Distillates,Inventor Stephan Ilnyckyj, which in turn is a continuation-impart ofSer. No. 835,587 filed Aug. 24, 1959, now abandoned entitled Process forthe Manufacture of Improved Pour Depres-' sants for Middle Distillates,Inventor, Stephan Ilnyckyj.

In accordance with the present invention, pour depressants of improvedpotency are secured by utilizing relatively small quantities ofmercaptans or carbon tetrachloride during the copolymerization step.

With the increase in the use of hydrocarbon fuels of all kinds, aserious problem has arisen in areas frequently subjected to lowtemperatures in the cold test characteristics of fuels. Particularly,serious problems have been encountered with heating oils and diesel andjet fuels that have too high a pour point, resulting either indistributional or operating difiiculties or both. For example, thedistribution of heating oils by pumping or syphoning is rendereddifiicult or impossible at temperatures around or below the pour pointof the oil. Furthermore, the flow of the oil at such temperaturesthrough the filters cannot be maintained, leading to the failure of theequipment to operate.

Also the low temperature properties of petroleum distillate fuelsboiling in the range between about 250 and about 750 F. have attractedincreasing attention in recent years because of the growth of market forsuch fuels in subarctic areas and because of the development ofturbo-jet aircraft capable of operating at altitudes where temperaturesof 50 F. or lower may be encountered.

It is, therefore, an object of the present invention to set forth animproved process for the manufacture of very effective pour depressantsfor middle distillates and lighter oils. In general, these oils boil inthe range from about 250 to 750F.

It is a still further object of the present invention to provide heatingoils, diesel fuel oils, kerosenes and jet fuels having low pour points.Aviation turbo-jet fuels in which the polymers may be used normally boilbetween about 250 and about 550 F. and are used in both military andcivilian aircraft. Such fuels are more fully defined by U.S. militaryspecifications MIL-F5 624C, MIL- F-25554A, MILF-25558A, and amendmentsthereto. Kerosenes and heating oils will normally have boiling rangesbetween about 300 and about 750 F. and are more fully described in ASTMspecification D-39648T and supplements thereto, where they are referredto as No. 1 and No. 2 fuel oils. Diesel fuels in which the polymers maybe employed are described in detail in ASTM specification D975-53T andlater versions of the same specification.

The process of the present invention produces copolymers of ethylene andup to about by weight of an olefinically unsaturated aliphatic monomercontaining from about 3 to 5 carbon atoms per molecule. In general,these compounds may comprise vinyl acetate, vinyl propionate, methylmethacrylate, allyl ethyl ether, divinyl ether, acrylonitrile,vinylacetonitrile and the like.

The preferred copolymers comprise ethylene-vinyl acetate copolyrner. Itis preferredthat the parts by weight of ethylene in the copolymer be inthe range from about to 99% as compared to parts by weight of vinylacetate in the range from about 40 to about 1%. A very desirablepolyethylene vinyl acetate copolymer contains about 15% to 28% by weightof vinyl acetate as, for example, about 20 parts by weight of vinylacetate.

The molecular weights of the ethylene-vinyl acetate copolymer arecritical and should be in the range from about 1,000 to 3,000,preferably in the range from about 1,500 to 2,200. The molecular weightsare determined by K. Rasts method (Ber. 55, 1051, 3727 (1922)).

The ethylene-vinyl acetate copolymer as described above is used in aconcentration in the range from about .001 to 0.2% by weight, preferablyin a concentration in the range from about .005 to 0.1% by weight.

In accordance with the present invention, the polymerization process isconducted in a solvent as, for example, toluene or hexane. It ispreferred, however, to use a benzene solvent. The initiator comprisesany peroxy compound, preferably di-tertiary-butyl-peroxide. Thetemperature of the polymerization reaction is in the range from about280 to 340 F. A very desirable temperature is about 300 F. The pressureis in the range from about 700 to 2,000 pounds, preferably 800 or 900pounds. The autoclave or similar equipment containing the solvent,initiator and vinyl acetate is purged with nitrogen, then with ethylenebefore charging with a sufiicient amount of ethylene to yield thedesired pressure when heated to the reaction temperature. During thepolymerization, additional ethylene is added to maintain the pressure atthe desired level. Polymerization is considered complete when thepressure drops less than 50 p.s.i.g. per hour. The product is strippedfree of solvent and unreacted vinyl acetate under vacuum.

The present invention maybe more fully understood by reference to thedrawing illustrating one embodiment of the same. Referring specificallyto the drawing, reactor 1 is first purged with nitrogen, introduced bymeans of line 2 and pump 3. Reactor 1 is then purged with ethyl: enewhich is introduced by means of line 2 and pump 3. Gases are removedfrom reactor 1 by means of line 4. The reactor is maintained at apositive pressure in the range from about 50 to pounds absolute.

Approximately 220 parts by weight of benzene is in- .troduced intoreactor -1 from benzene storage 5 by means of line 6 and pump 7. Reactor1 is then raised to a temperature of 300 F. by means of heating element8 Wherein a heating fluid or equivalent is introduced by means of line 9and withdrawn by meansof line 10. Reactor 1 is held at 300 F. during thecourse of the reaction by the removal of heat or by the addition of heatthereto. Ethylene is introduced by means of line 2 so as to raise thepressure of the reactor to about 900 pounds.

The addition of vinyl acetate and of di-tertiary-butylperoxide isstarted concurrently. The vinyl acetate is withdrawn from storage zone11 and introduced into the reactor by means of line 12 and pump 13.Approximate-1y 55 parts by weight of vinyl acetate is added over a twohour period. The peroxide is introduced by passing benzene into storagezone 14 by means of line 15 and then introducing the solution into thereactor 1 by means of line 16 and pump 17. Approximately 5.5 parts byweight of peroxide are combined with 16.5 parts by weight of benzene.The resulting 22 parts by weight of 25% peroxide solution in benzene isadded to reactor 1 over a three hour period.

In accordance with the present invention, during the addition of thevinyl acetate a mercaptan as, for example, dodecyl mercaptan iscontinuously added by means of line 18. The amount of mercaptan added tothe reaction mixture is such as -to yield .02 to .4 wt. percent,preferably .1 to .2 wt. percent of mercaptan sulfur per total amount ofvinyl acetate used in the copolymerization.

After the addition of the peroxide has been completed, the reactor isheld for an additional one-half hour at a temperature of about 300 F.The ethylene is added continuously so as to maintain the pressure atabout 900 pounds. In operation, approximately 934 parts by weight byvinyl acetate are used in conjunction with from about 2,800 to 3,800parts by weight of ethylene.

At the end of the reaction, the reactor is allowed to cool to about 160F. and the reaction product is withdrawn by means of line 19 and passedinto separation zone 20. Excess ethylene is removed overhead fromseparation zone 20 by means of line 21. The polymer product comprisingthe copolymer in a benzene solution may be withdrawn by means of line 22and further handled as desired. Under certain instances, it may bedesirable to separate at least a portion of the benzene from thecopolymer. Under these conditions, the benzene copolymer product ispassed to separation zone 23- -by means of line 24. Benzene is removedoverhead by means of line 25, while a copolymer product is withdrawn bymeans of line 26. i

The quantity mentioned above may be somewhat varied. For example, basedupon 55 parts by weight of vinyl acetate, the amount of benzene utilizedmay vary from about 180 to 300 parts by weight, and the amount ofdi-tertiary-butyl-peroxide may vary from about 3 to 8 parts by weight.Also as mentioned, the amount of ethylene utilized varies from about2,800 to 3,800 parts by weight, or approximately 938 parts by weight ofvinyl acetate. The time of reaction also may be varied from about 2 to 4hours, depending upon other operating variables.

In order to further illustrate the invention, a number of operationswere conducted in accordance with the above described technique. Theresults of these operations are illustrated in the following table:

per total amount of vinyl acetate used in the copolymerizationl Thus,when utilizing dodecyl mercaptan, the amount used is a concentrationequal to 0.1 to 2.0 wt. percent, preferably 0.5 to -1.0 wt. percent ofthe total amount of vinyl acetate used in the copolymerization.

In accordance with the present invention, the reactants are preferablyadded continuously to the reactor, as described above.

What is claimed is:

1. Process for the manufacture of a pour depressant comprising acopolymer of ethylene and an aliphatic vinyl monomer which comprisesreacting ethylene and said monomer in a benzene solvent at a temperaturein the range of from about 280 to 340 F. and at a pressure in the rangefrom about 700 to 2,000 pounds under conditions wherein theconcentration of the vinyl monomer in the solvent solution varies fromabout 4 to 14%, whereby a polymer having a molecular weight in the rangefrom about 1,000 to 3,000 is secured and wherein the concentra tion ofthe vinyl acetate in the product will vary from about 1 to 40% andadding to said benzene solvent an aliphatic mercaptan containing fromabout 1 to 18 carbon atoms in the molecule in a concentration to yield.02 to .4 wt. percent of mercaptan sulfur per total amount of vinylacetate used in the copolymerization.

2. Process as defined by claim 1 wherein the concentration of the vinylmonomer in the solvent solution varies from about 4 to 7 /2%, wherebythe concentration of the vinyl monomer in the product will vary fromabout 15 to about 25%.

3. Process for the manufacture of a pour depressant comprising acopolymer of ethylene and an aliphatic vinyl monomer which comprisesreacting ethylene and said monomer in a benzene solvent at a temperaturein the .range of from about 280 to 340 F. and at a pressure in the rangefrom about 700 to 2,000 pounds under conditions wherein theconcentration of the vinyl monomer in the solvent solution varies fromabout 4 to 14%, whereby a polymer having a molecular weight in the rangefrom about 1,000 to 3,000 is secured and wherein the concentration ofthe vinyl acetate in the product will vary from about 1 to 40% andadding to said benzene solvent a modifier selected from the groupconsisting of carbon tetrachloride and an aliphatic mercaptan containingfrom about 1 to 18 carbon atoms in the molecule, said modifier beingpresent in a concentration of from about 0.33 to 1.0% by volume basedupon the vinyl acetate.

Efiecl of dodecyl mercaptan and carbon tetrachloride on quality of thepour depressant [Conditions of copolymerization: 1800 ml. of benzene,300ml. of vinyl acetate over 3 hours, 30 ml. of Di-t-butyl peroxide over3% hours, 900 p.s.i.g., 300 F., total reaction time 3% hours] ModifierNone Dodeeyl Mercaptan Carbon Tetrachloride Modifier in Vinyl Acetate,vol. percent- Nil 0. 33 1. 0 2. 0 4. 0 0. 33 1. 0 2. 0 Yield, g 797 750738 679 541 715 699 662 Vmyl'Acetate, wt. percent--. 29. 0 27. 0 30. 630. 7 34. 0 24. 6 27.1 Molecular Weight 2, 700 2, 950 2, 685 1, 750 2,440 2, 475 1, 800 Viscosity at 100 F., es 150 130 11 161 180 161 FourDepression, F.:

With 0.015 Wt. percent 65 15 45 45 25 With 0.025 wt. percent 50 85 85 85'25 7O 45 1 50/50 solution of copolymer in 400500 F. naphtha. 2 In a50/50 blend of virgin and cracked gas oils, ASTM pour 20 F.

4. Process as defined by claim 1 wherein said mercaptan contains fromabout 10 to 14 carbon atoms in the molecule.

5. Process as defined by claim 1 wherein the time period is in the rangefrom about 2 to 6 hours, wherein the temperature is in the range of fromabout 290 to 310 F., wherein the pressure is in the range from about 650to 1,000 pounds, and wherein the concentration of the vinyl acetate in abenzene solution varies from about .53 to about 10%.

'6. Process as defined by claim 1 wherein the reaction is preferably 0.1to 0.2 Wt. percent of mercaptan sulfur initiated byape'roxy compound,di-tertiary-butyl-peroxide.

7. Process as defined by claim 1 wherein the reaction is carried out inan autoclave which is purged with nitrogen, then with ethylene and thencharged with a sufficient amount of ethylene to yield the desiredpressure when heated to the reaction temperature.

8. Process as defined by claim 1 wherein addition ethylene is added tothe reaction mixture whenever the pressure drops by about 100 p.s.i.g.

9. Process as defined by claim 1 wherein unreacted vinyl acetate isstripped under vacuum when the reaction is completed.

10. Process as defined by claim 1 wherein saidaliphatic mercaptan isdodecyl mercaptan.

11. Process as defined by claim 3 wherein the modifier consistsessentially of carbon tetrachloride present in a concentration of about.331.0% by volume based upon the volume of vinyl acetate present.

6 References Cited by the Examiner UNITED STATES PATENTS 2,395,3812/1946 Squires 26087.3 2,3 96,785 3/1946 Hanford 260-873 2,947,7358/1960 Bartl 260-873 3,093,623 6/1963 Ilnyckyj 26087.3

OTHER REFERENCES Wiles et al.: Industrial and Engineering Chemistry,vol.

10 41, N0. 8, pp. 1679-1682.

Schildknecht: Vinyl and Related Polymers, pp. 106 and 504, Wiley (1957).

JOSEPH L. SCHOFER, Prirnary Examiner.

15 LOUISE P. QUAST, JOSEPH R. LIBERMAN, WIL- LIAM H. SHORT, Examiners.

JOHN F. MCNALLY, Assistant Examiner.

1. PROCESS FOR THE MANUFACTURE OF A POUR DEPRESSANT COMPRISING ACOPOLYMER OF ETHYLENE AND AN ALIPHATIC VINYL MONOMER WHICH COMPRISESREACTING ETHYLENE AND SAID MONOMER IN A BENZENE SOLVENT AT A TEMPERATUREIN THE RANGE OF FROM ABOUT 280* TO 340*F. AND AT A PRESSURE IN THE RANGEFROM ABOUT 700 TO 2,000 POUNDS UNDER CONDITIONS WHEREIN THECONCENTRATION OF THE VINYL MONOMER IN THE SOLVENT SOLUTION VARIES FROMABOUT 4 TO 14%, WHEREBY A POLYMER HAVING A MOLECULAR WEIGHT IN THE RANGEFROM ABOUT 1,000 TO 3,000 IS SECURED AND WHEREIN THE CONCENTRATION OFTHE VINYL ACETATE IN THE PRODUCT WILL VARY FROM ABOUT 1 TO 40% ANDADDING TO SAID BENZENE SOLVENT AN ALIPHATIC MERCAPTAN CONTAINING FROMABOUT 1 TO 18 CARBON ATOMS IN THE MOLECULE IN A CONCENTRATION TO YIELD.02 TO .4 WT. PERCENT OF MERCAPTAN SULFUR PER TOTAL AMOUNT OF VINYLACETATE USED IN THE COPOLYMERIZATION.
 3. PROCESS FOR THE MANUFACTURE OFA POUR DEPRESSANT COMPRISING A COPOLYMER OF ETHYLENE AND AN ALIPHATICVINYL MONOMER WHICH COMPRISES REACTING ETHYLENE AND SAID MONOMER IN ABENZENE SOLVENT AT A TEMPERATURE IN THE RANGE OF FROM ABOUT 280* TO340*F. AND AT A PRESSURE IN THE RANGE FROM ABOUT 700 TO 2,000 POUNDSUNDER CONDITIONS WHEREIN THE CONCENTRATION OF THE VINYL MONOMER IN THESOLVENT SOLUTION VARIES FROM ABOUT 4 TO 14%, WHEREBY A POLYMER HAVING AMOLECULAR WEIGHT IN THE RANGE FROM ABOUT 1,000 TO 3,000 IS SECURED ANDWHEREIN THE CONCENTRATION OF THE VINYL ACETATE IN THE PRODUCT WILL VARYFROM ABOUT 1 TO 40% AND ADDING TO SAID BENZENE SOLVENT A MODIFIERSELECTED FROM THE GROUP CONSISTING OF CARBON TETRACHORIDE AND ANALIPHATIC MERCAPTAN CONTAINING FROM ABOUT 1 TO 18 CARBON ATOMS IN THEMOLECULE, SAID MODIFIER BEING PRESENT IN A CONCENTRATION OF FROM ABOUT0.33 TO 1.0% BY VOLUME BASED UPON THE VINYL ACETATE.